1. Field of the Invention
This invention relates to acid treated polyurethane foam end wraps for use in the cold permanent waving of hair. Further, the invention relates to the process of using the treated end wraps in cold permanent waving.
2. Prior Art
Cold permanent waving of hair has been a popular means of waving hair for a number of years. This popularity is due to the greater convenience for this method over other methods where externally applied heat is needed to achieve the desired result. This additional convenience has permitted nonprofessional consumers to wave their hair in their own homes. In cold waving, the waving is accomplished by applying a reducing agent to the hair which causes the hair to be "softened" (the disulfide linkages present in the keratin of hair are broken). This reducing step may be done after the hair has been sectioned into individual tresses but before it has been rolled onto curlers, after the rolling has been accomplished or at both times. After sufficient time has elapsed the hair is rinsed and neutralized by chemical or air oxidation, which step reforms the disulfide linkages broken in the aforementioned reducing step.
Cold permanent waving is not without its problems however. The materials are oftentimes somewhat difficult to use with the desired result not always achieved. For example, the ends of the hair present particular problems from a handling point of view, as well as from a hair damage point of view. In the waving process, the free ends of the hair must be wound about a cylindrical body (a curler) and this presents some difficulty. To overcome this problem most commercial waving kits contain small square or rectangular pieces of paper or other material (end wraps) which are folded and placed around a hair tress in such a manner that they embrace the free end of the tress.
Among the types of materials which have been used for the end wrap are permeable polyester and polyether polyurethanes as disclosed by Haefele in U.S. Pat. No. 3,345,993, issued Oct. 10, 1967; impermeable polyester and polyether polyurethane as disclosed by Haefele in U.S. Pat. No. 3,465,759, issued Sept. 9, 1969; and paper as disclosed by Bonilla in U.S. Pat. No. 2,991,790, issued July 11, 1961. Of these materials, permeable polyurethane foams prepared by condensation of organic isocyanates with polyols are especially useful. Such polyurethanes have excellent solvent resistance, and color stability in the presence of ultraviolet light.
All of these types of end wraps which have been disclosed in the prior art are well known to be helpful in the winding process. However, they do not fully protect the ends of the hair. The desirability of protecting the ends of the hair in permanent waving stems from the fact that repeated use of conventional waving procedures is often accompanied by an overexposure of the hair ends which are susceptible to damage because of the age of the hair at the ends and the stress the ends are expose to during the winding process. Such ends, when subjected to renewed cold waving treatments, generally exhibit undue frizziness, curling, harshness and dryness because frequent treatment is believed to unduly stress and overexpose the hair ends in renewing or repeating the waving process.
There have been attempts in the past to treat certain types of end wraps with chemical agents so that the waving solution is counteracted before reaching the hair ends (See, for example, the aforementioned Bonilla reference). Also included in some prior art attempts was the treatment of paper end wraps with citric acid to counteract the waving solution and thereby protect hair ends.
While it would be highly desirable to treat end wraps of the preferred polyurethane materials with waving solution counteractant, certain of such common counteractant chemicals are not compatible with all types of end wrap polyurethane. Some agents such as citric acid, for example, tend to degrade and discolor polyester polyurethane. The concurrently filed application of Adrion and Hartsough having Ser. No. 670,594 is directed toward particular preferred acid treated polyester polyurethane end wraps. There is, however, a continuing need to identify and select compatible materials for use in realizing preferred treated end wraps for cold permanent waving products and methods.
Accordingly, it is an object of this invention to provide effective acid treated end wraps which are useful in the keratin modification process.
It is a further object of this invention to provide such treated end wraps which are made with preferred compatible end wrap and acid treatment materials.
It is a further object to provide an improved method for permanently waving hair by utilizing treated end wraps made from preferred materials.
It has been surprisingly discovered that by selecting polyether polyurethane end wraps for treatment with weak carboxylic acids, the above objectives can be realized and end wraps prepared which are superior to similar articles of the prior art.